1. Field of the Invention
The invention relates in general to an adjustable lens module, and more particularly to an adjustable lens module and an image projector applied with the same.
2. Description of the Related Art
Home theater systems are gaining wider popularity. The image projector used in a home theater, such as a back projection TV for instance, is mainstream. Therefore, how to produce an image projector for meeting the consumer's high requirement has become an imminent challenge to the manufacturers.
An image projector mainly includes a light source, an optical assembly, an imaging device and a lens module. The image projector functions by enabling the beam of light generated by the light source to be projected to the imaging device via the optical assembly, and then the beam of light is further reflected to the lens to generate an image. The optical assembly includes a color wheel, a condenser and a fold mirror. Examples of the imaging device include a digital micro-mirror device (DMD) and a liquid crystal display (LCD) panel. A DMD has on its surface several hundred thousand microscopic mirrors arranged in a rectangular array which correspond to the pixels in the image to be displayed. When the image projector functions, the optical path from the light source to the imaging device has to be correct, so that the luminance region generated when the beam of light is projected to the imaging device overlaps with the imaging device, enabling the image of the imaging device to be completely projected onto a screen via a lens of the lens module.
A precise optical path can be found to assure that the luminance region is substantially overlapped with the imaging device if the optical components of the image projector are appropriately incorporated. However, after the optical components are assembled, the tolerance of an optical component may differ with one another and needs to be compensated before image can be clearly and completely projected onto the screen via the imaging device and lens.
In a conventional image projector, the lens is received within a lens barrel. The lens barrel is covered by a housing, thereby mounting the lens barrel on the frame of the image projector. The method of mounting the housing on the frame is achieved by applying several fasteners to the flange of the housing so that the housing is fixed to the frame of the image projector. That is, the lens is no more adjustable once fixed. Since the lens can not be adjusted in the conventional design, the tolerance can not be compensated.
Therefore, it is necessary to provide an adjustable lens module whose lens can be quickly and easily adjusted to compensate the tolerance between the optical components, thereby saving the required time and labor. After the tolerance is compensated, the central axis of the lens is substantially parallel to or overlapped with the optical axis of the lens to receive the beam of light precisely. Consequently, the image can be completely and precisely projected onto the screen via the imaging device and lens.